Breast cancer is very common but therapeutic options to treat this disease are limited. Metastasis, the process via which breast tumor cells disseminate to the lung, brain and other tissues, is the most dangerous aspect of breast cancer yet there are few therapeutics that inhibit this process. Recent studies strongly suggest macrophages activate migration of breast tumor cells and the early stages of metastasis. Acordingly, Vala Sciences proposes an assay system to test compounds on breast tumor cell:macrophage interactions relevant to initiation of metastasis. The system (Tumor Cell Macrophage Assay or TCMA) will be high throughput (96-well format or greater) and utilize high content methods (automated quantitative digital microscopy and cell image analysis). For PhaseI, Vala Sciences will develop methods for preparing the tumor cells (grown in 3-D spheroids) and macrophages (differentiated to the M2 phenotype) for use in the assay, and, additionally, develop the basic methods for conducting the assay, including establishing the well configuration, time-course, hypoxic conditions, use of chemotaxic agents, and the basic methods for image acquisition and analysis.